This invention relates to novel protease inhibitors and in particular to inhibitors of the aspartate protease possessed by certain retroviruses, notably HIV. The invention further relates to the use of such protease inhibitors in the treatment of conditions caused by retroviruses and in the preparation of medicaments for this purpose. The invention also relates to novel synthesis methodology for the facile preparation of protease inhibitors and similar chemical structures.
Many biological processes are dependent upon the accurate enzymatic abscission of polypeptides at particular amino acid sequences. An example of such an operation is the post-translational processing of the gag and gag-pol gene products of the human immunodeficiency virus HIV to allow for the organisation of core structural proteins and release of viral enzymes. The enzyme responsible for this task, HIV protease, is a virally encoded homodimeric protease belonging to the aspartic protease family of enzymes. The human renin and pepsin enzymes also belong to this family. Inhibition of the HIV protease in cell culture prevents viral maturation and replication and thus this enzyme represents an attractive target for antiviral therapy against HIV in humans.
There are several references in the patent literature describing inhibitors of HIV protease, typically peptidomimetics having a large number of chiral centres. For example, Abbott Laboratories have extensively investigated linear peptidomimetics as described in a series of patent publication commencing with EP 402 654 and culminating in Abbott""s application no. WO 94 14436 describing optimized linear peptidomimetics and in particular the compound Ritonavir: 
Norvir as this compound is now known, is registered by the FDA and although it has good clinical efficacy, its synthesis is arduous. The synthesis difficulties which have characterized prior art protease inhibitors can be understood by referring to Roche""s protease inhibitor saquinavir (Inverase): 
According to literature reports, this compound requires a synthesis route of some 20 steps resulting in an overall yield reputed to be around 2%. This difficult synthetic availability will put pressure on treatment cost and production capacity.
Merck""s U.S. Pat. No. 5,413,999 describes indanyl pentamine compounds, including its currently marketed product indinavir: 
Merck""s EP 480 714 discloses a symmetric protease inhibitor having terminal indanolamine groups spaced by a 7 carbon backbone: 
These compounds are prepared by complex methodology starting from an alkenediol.
Banyu""s Japanese patent application no 7242613 A also describe symmetric protease inhibitors having indanolamine terminal groups spaced by a 7-carbon backbone: 
where R is H or lower alkyl. These compounds are prepared by BuLi-alkylation of N,O-isopropylidine-N-[2(R)-hydroxy-(1S)-indanyl]-3-phenylpropanamide with 2-chloro-2-chloromethyl-propene, followed by ozonation, reduction and deprotection.
Vertexxe2x80x2 international patent application no WO 94/13629 explores the use of a mannitol carbohydrate precursor to prepare compounds of the formula: 
It will be apparent that with these inhibitors, the benzoyl moieties esterified to the C-1 and C-6 hydroxy groups of the mannitol precursor are intended to fill the P1 and P1xe2x80x2 pockets of the HIV protease active site. Amino acid functions, such as valyl, are amide bonded to the C-2 and C-5 hydroxy groups and are intended to fill the P-2 and P-2xe2x80x2 pockets of the enzyme. These compounds are prepared by bridging the 3-and 4-hydroxy groups with isopropylidine, epoxidising and ring opening the terminal hydroxy groups with a nucleophile such as aryl alcohol followed by amidation of the resulting free hydroxy groups with a respective amino acid. Alternatively the isopropylidine-protected mannitol is first amidated on the more active C-1 and C-6 (terminal) hydroxy groups with the amino acid P-2 filling groups and then esterified with the benzoyl moities on the C-2 and C-5 hydroxy groups.
One of Abbott Laboratories"" early patent publications in the protease field, EP 402 646, describes a great number of potential approaches to the construction of protease inhibitors. One of these approaches also employs a carbohydrate precursor which becomes the central backbone of a symmetric protease inhibitor. Examples 305 and 307 of EP 402 646 describe the ring-opening of a mannosaccharodilactone and the addition of terminal valine esters to form a 3,4-O-isopropylidine-bridged adipamide derivative. The aryl groups which are to fit into the P1 and P1xe2x80x2 pockets of the protease are added subsequently via triflate activation at the C-2 and C-5 positions of the carbohydrate backbone and these are later converted to phenylthio groups before the isopropylidine bridge is removed. 
The drawbacks with this process are the inevitable inversion of the configurations of C-3 and C-4 and that while reagents such as thiophenyl can be used to displace the triflate leaving group in the manner shown in EP 402 646, this can only produce thioether derivatives for the P1 and P1xe2x80x2 filling groups. At a superficial level it could be thought that the triflate leaving group could be displaced with conventional alkylating reagents such as alkoxide to give an O-alkylated P1/P1xe2x80x2 filling group. However we have discovered in this prior art process that the use of alkoxide tends to eliminate the triflates producing an olefin, instead of the desired O-alkylated substituent.
Magnus Bjxc3x6rsne et al in xe2x80x9cSynthesis of Potential Candidates for Therapeutic Intervention against the Human Immunodeficiency Virusxe2x80x9d, Stockholm University, 1995 describes the compound 
the corresponding benzyl ester and the phenylalanine analog. These compounds are prepared from an L-mannaric acid precursor via the steps of
i) bridging the C-3 and C-4 hydroxyls of the hexitol with isopropylidine,
ii) protecting the C-1 and C-6 primary hydroxyls,
iii) O-alkylating the C-2 and C-5 hydroxyls to the aralkyl ethers,
iv) oxidating the C-1 and C-6 primary hydroxyls to carboxylic acids; and
v) condensing the resulting compound with the appropriate amino acid (ester) terminal groups. This methodology may be graphically represented as follows: 
The appropriate valine or phenylalanine (ester) end unit is then condensed onto the terminal carboxyls in dichloromethane-THF using HOBt-EDC coupling conditions. Despite the need for protection, oxidation and deprotection steps., the Bjxc3x6rsne synthesis methodology is an improvement over the very large number of steps in conventional peptidomimetic synthesis (see the discussion of saquinavir above). The Bjxc3x6rsne process also avoids the triflate activation, the preferential reactivity of the xe2x80x9cwrongxe2x80x9d C-3 and C-4 atoms and other drawbacks of the Abbott EP 402 646 process. However the compounds proposed by Bjxc3x6rsne have inadequate antiviral properties. The best Bjxc3x6rsne compound, where the terminal amines are valine methyl esters (depicted above), has an IC50 of 5 xcexcM which should be compared to currently marketed protease inhibitors which have IC50 values one or more orders of magnitude lower.
We have now discovered a novel group of compounds with antiviral properties in the nanomolar IC50 range and which lend themselves to a novel carbohydrate based synthesis technique which is even more convenient than those of the prior art discussed above.
Accordingly, a first aspect of the invention provides novel compounds of the formula 
wherein:
Axe2x80x2 and Axe2x80x3 are independently a group of the formula II: 
wherein:
Rxe2x80x2 is H, CH3, C(CH3)2, xe2x80x94ORa, xe2x80x94N(Ra)2, xe2x80x94N(Ra)ORa or -DP
Rxe2x80x2xe2x80x3 is H, CH3; Ra is H, C1-C3 alkyl;
D is a bond, C1-3 alkylene, xe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94S(O)xe2x80x94 or xe2x80x94S(O)2xe2x80x94;
P is an optionally substituted, mono or bicyclic carbo- or heterocycle;
Rxe2x80x3 is H, any of the sidechains found in the natural amino acids, carboxacetamide, or a group (CH2)nDP;
M is a bond or xe2x80x94C(xe2x95x90O)N(Rxe2x80x2xe2x80x3)-;
Q is absent, a bond, xe2x80x94CH(OH)xe2x80x94 or xe2x80x94CH2xe2x80x94;
or Rxe2x80x3 together with Q, M and Rxe2x80x2 define an optionally substituted 5 or 6 membered carbo- or heterocyclic ring which is optionally fused with a further 5 or 6 membered carbo- or heterocyclic ring;
with the proviso that Rxe2x80x2 is xe2x80x94ORa, xe2x80x94N(CH3)2, xe2x80x94N(Ra)ORa or -DP if M is a bond and Q is absent;
X is H, OH, OCH3;
Y is H, OH, OCH3, but X and Y are not both H;
Zxe2x80x2 and Zxe2x80x3 are independently xe2x80x94(CH2)mP where P is as defined above;
n and m are independently 0,1 or 2;
and pharmaceutically acceptable salts and prodrugs thereof.
Compounds of the formula I are active inhibitors of aspartyl proteases, such as those from HIV. Further aspects of the invention thus provide:
a pharmaceutical formulation comprising a compound of the formula I in admixture with a pharmaceutical acceptable carrier or diluent;
the use of a compound of the formula I in the manufacture of a medicament for the prophylaxis or treatment of conditions, such as AIDS caused by retroviruses, such as HIV; and
a method for treating conditions caused by retroviruses, especially AIDS in humans, comprising administering a compound of formula I to a subject afflicted with said condition.
The compounds have a relatively low molecular weight and should therefore provide good oral absorption properties in mammals. In contrast to prior art aspartyl protease inhibitors, the compounds of the invention can be conveniently prepared with a small number of steps from readily available and cheap starting materials, such as L-mannarodilactone or its commercially available precursors or derivatives, such as L-mannonic-xcex3-lactone.
A further aspect of the invention thus provides a method for the preparation of a compound of the formula I 
where X, Y, Zxe2x80x2 and Zxe2x80x3 are as defined above and each of Axe2x80x2 and Axe2x80x3 are independently: a group of the formula II or a conventional protease P-2/P-2xe2x80x2 filling group, the method comprising
i) O-alkylation of an L-mannaric-1,4:6,3-di-lactone to form the Zxe2x80x2 and Zxe2x80x3 groups,
ii) opening of the lactone with similar or different primary or secondary amines to form the respective Axe2x80x2 and Axe2x80x3 groups; and
iii) optional conversion of the C-3 and C-4 to the appropriate X and Yxe2x80x3 groups.
An example of this method aspect of the invention can be depicted as follows: 
The method aspect of the invention is preferably used to produce the compounds of formula I as claimed herein, but can also be used to prepare protease inhibitors with conventional protease P-2/P-2xe2x80x2filling groups.
Introduction of the Zxe2x80x2 and Zxe2x80x3 groups as ethers of the C-2 and C-5 hydroxyls in step i) is conveniently carried out by O-alkylation with the appropriate derivative: E(CH2)nP where E is a halogen, mesylate, tosylate etc. and P and n are as described above in the presence of a base such as a carbonate, metal hydride or hydroxide and an aprotic solvent such as N,N-dimethylformamide, tetrahydrofuran or acetone. Conveniently the alkylating agent is benzyl trichloroacetimidate in conjunction with a proton or a Lewis acid, e.i. trimethylsilytriflate.
The ring opening in step ii) to introduce the amino or amino acid derivatives Axe2x80x2 and Axe2x80x3 are carried out using standard conditions in solvents such as dioxane, nitromethane THF, diglym, DMF or DMSO, which are preferably chosen to dissolve both the carbohydrate derivative and the particular amine involved.
For ease of synthesis it is generally preferred that the terminal amines Axe2x80x2 and Axe2x80x3 are identical. However, although the target enzyme is a symmetric dimer, thus implying a tight interaction with symmetric compounds, it can in some circumstances be advantageous for resistance or pharmacokinetic reasons etc. to have asymmetric terminal amines. Where is it is desired to have an asymmetric compound, that is where the Axe2x80x2 and Axe2x80x3 groups differ, it will generally be most convenient to add the respective Axe2x80x2 and Axe2x80x3 groups sequentially. This can be done in conjunction with appropriate protection of one of the rings of the dilactone, but may also be achieved by manipulation of the reagent concentrations, reaction conditions, speed of addition etc. to provide a monoaminated lactone which is separated by conventional techniques or amine neutralization, prior to reaction with the second Axe2x80x2 or Axe2x80x3 amine.
Alternatively the differential terminal amination can be achieved with a solid phase synthesis where the unaminated or partially aminated lactone is secured to a solid phase substrate, such as polymer beads of which many are known in solid phase chemistry, for instance Merrifield resin. Immobilization of the lactone in this fashion will only allow amination on a defined lactone ring. Scheme I below outlines such a scheme in the context of combinatorial synthesis of a library of compounds in accordance with the invention, but it will be apparent that single pure compounds can be prepared by similar methodology, but using pure reagents. 
In Scheme 1, steps 1 and 2 comprise the preparation of a linking group on the carboxy groups of the resin beads. Linkers of various lengths, rigidities and differential cleavabilities (several are listed against step 2) can be used as is conventional in the solid phase chemistry art. In step 3, the free amine on the linker-equipped solid phase bead is amide bonded with an N-protected amino acid under standard peptide chemistry conditions. The amino acid reagent comprises a number of different, protected amino acids, such as N-Boc valine, N-Boc isoleucine, N-Boc alanine, N-Boc leucine etc. and thus this reaction step results in a first combinatorial chemistry tier. The solid phase beads now bear a plurality of randomly disposed amino acids each spaced by a respective linker from the carboxy surface of the bead.
In step 4 the free amine (after deprotection of the N-Boc groups) on the amino acid array is used to ring-open a di-O-alkylated y-dilactone, wherein Rx and Ry are the same or different optionally substituted (hetero)arylalkyl groups, for instance benzyl, fluorobenzyl, pyridylmethyl etc. This ring opening is carried out under conventional conditions, as exemplified below, in solvents such as dioxane, nitromethane, THF, diglym, DM, DMSO and the like. If Rx and Ry are different (hetero)arylalkyl groups, this step will thus produce a further tier of combinatorial variation, depending on whether the Rx- or Ry-bearing ring is opened. However, the dilactone reagent itself may comprise a plurality of different dilactones with various combinations of Rx, Ry and/or stereochemistry of the lactone, leading to an even greater spread of combinatorial diversity.
In the fifth step, the remaining ring of the now-immobilized lactone is ring opened in a corresponding fashion with a further amine reagent. Once again this amine reagent may comprise a mixture of different amines, for instance L-amino acids or (hetero)cyclic amines such as the one depicted. Thus this step too may create a further tier of combinatorial diversity. The combinatorial library is cleaved from the linker using its appropriate cleavage reagent, typically a specific amidase or change in pH etc.
Although the compounds of formula I are preferably prepared by the method aspect of the invention, it is also possible to employ the initial steps of the Bjxc3x6rsne technique described above in conjunction with the appropriate choice of Axe2x80x2 and Axe2x80x3 amines, followed where necessary by postmodification of X and Y as discussed above and exemplified in the following Example 2.
Preparation of compounds of Formula I in which X is hydrogen can be conveniently done by deoxygenation as illustrated in the accompanying Examples 2 and 26. The preferred stereochemistry is the 2R, 3R, 4R, 5R form.
Carbocyclic groups for Rxe2x80x2 as -DP and/or Zxe2x80x2/Zxe2x80x3 and/or the optional substituents thereto may be saturated, unsaturated or aromatic and include monocyclic rings such as phenyl, cyclohexenyl, cyclopentenyl, cyclohexanyl, cyclopentanyl, or bicyclic rings such as indanyl, napthyl and the like.
Heterocyclic groups for Rxe2x80x2 as -DP and/or Zxe2x80x2/Zxe2x80x3 and/or the optional substituents thereto may be saturated, unsaturated or aromatic and have 1 to 4 hetero atoms including monocyclic rings such as furyl, thienyl, pyranyl, pyrrolyl, pyrrolinyl, pyrrolidinyl, pyrazolyl, pyrazolinyl, pyrazolidinyl, imidazolyl, imidazolinyl, imidazolidinyl, pyridyl, piperidinyl, pyrazinyl, piperazinyl, pyrimidinyl, pyridazinyl, oxazolyl, oxazolidinyl, isoxazolyl, isoxazolidinyl, morpholinyl, thiazolyl, thiazolidinyl, isothiazolyl, isothiazolidinyl, and the like or bicyclic rings especially of the above fused to a phenyl ring such as indolyl, quinolinyl, isoquinolinyl, benzimidazolyl, benzothiazolyl, benzoxazolyl, benzothienyl etc. The carbo or heterocyclic ring may be bonded via a carbon or via a hetero atom, typically a nitrogen atom, such as N-piperidyl, N-morpholinyl etc.
Preferred embodiments of Formula II for the Axe2x80x2/Axe2x80x3 groups of the compounds of the invention include those of the formula IIa or IIe: 
where n is 1 or 2 and Rxe2x80x2 is alkyloxy, preferably methyloxy, or those where n is 0 and Rxe2x80x2 is methyl.
Other preferred groups of formula II include IIb below 
An alternative preferred configuration for the Axe2x80x2/Axe2x80x3 groups of the compounds of the invention includes groups of the formula IIc: 
where Q is a bond, methylene or xe2x80x94C(OH)xe2x80x94 and Rxe2x80x2 is xe2x80x94ORa, xe2x80x94N(Ra)2, xe2x80x94NRaORa, where Ra is H or C1-C3 alkyl, or a carbo- or heterocyclic group including N-piperidine, N-morpholine, N-piperazine, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrimidyl, is pyrazinyl etc.
A favoured subset of compounds within formula IIc has the formula IId: 
where Rd is hydrogen or methyl (that is a valyl or isoleucyl side chain) and Re is 
where X is methylene, O, S, Sxe2x95x90O, S(xe2x95x90O)2 or NH or Re is xe2x80x94N(CH3)2, xe2x80x94NHOH, xe2x80x94NHOMe, xe2x80x94NHOEt, xe2x80x94NMeOH, xe2x80x94NMeOMe etc.
In each of formulae Ia, IIb and IIc, Rxe2x80x3 is hydrogen, methyl, ethyl, isopropyl, cycloalkyl such as cyclopropyl, cyclobutyl or cyclohexyl, cycloalkenyl, benzyl, carboxacetamide or 4-imidazolylmethy, any of which may be substituted as defined above. Preferred Rxe2x80x3 groups include the side chains found in the natural amino acids, especially those of leucine, asparagine, histidine or proline. The most preferred Rxe2x80x3 groups for formula Ia, IIb, IIc and IId are the isoleucyl and especially the valyl side chain.
Rxe2x80x2 will vary depending on the nature of Q and/or M, if present, and may for instance be selected from hydrogen, methyl, ethyl, isopropyl, Re as defined above, valinol, a heterocycle such as pyridyl, thiazole, oxazole, imidazole, N-piperidine, N-morpholine, N-piperazine, pyrrolyl, imidazolyl, pyrazolyl, pyrimidyl, pyrazinyl, any of which Rxe2x80x2 groups may be substituted as defined for Zxe2x80x2/Zxe2x80x3 below.
Further favoured Axe2x80x2/Axe2x80x3 groups include those of formula II where Rxe2x80x3, Q, M and Rxe2x80x2 together define an optionally substituted 5 or 6 membered carbo- or heterocylic ring. A preferred group within this definition include groups within formula III: 
where
Rxe2x80x2xe2x80x3 is as defined above,
Rxe2x80x2 is H, NR4R4, C(xe2x95x90O)R3, CR3R4 or a monocyclic, optionally substituted carbo- or heterocycle;
R2 is OH, or together with Rxe2x80x2 is xe2x95x90O, or if Rxe2x80x2 is NR4R4, then R2 may be H;
R3 is H, halo, C1-C3 alkyl, OR5, NR4R4;
R4 is H, C1-C3 alkyl;
R5 is H or a pharmaceutically acceptable ester;
R6 is OH, NH2, carbamoyl or carboxy;
R7 is hydrogen, C1-C4 straight or branched alkyl or together with the adjacent carbon atoms forms a fused phenyl or heteroaromatic ring;
Preferred groups of formula III include aminoindanol and 1-amino-azaindan-2-ol, that is moieties of the formulae: 
Conventional protease P-2/P-2xe2x80x2 filling groups for Axe2x80x2/Axe2x80x3 include those found in Roche""s saquinavir and Abbott""s ritonavir compounds. Additional examples of conventional P-2/P-2xe2x80x2 filling groups include those found in Vertexxe2x80x2 VX 478, Agouron""s AG1343 (now known as nelfinavir) and Merck""s indinavir, as depicted above.
Optional substitutents for the carbo- or heterocyclic moiety of Zxe2x80x2/Zxe2x80x3 or Axe2x80x2/Axe2x80x3 include one to three substituents such as halo, amino, mercapto, oxo, nitro, NHC1-C6 alkyl, N(C1-C6 alkyl)2, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 alkanoyl, C1-C6 alkoxy, thioC1-C6 alkyl, thioC1-6 alkoxy, hydroxy, hydroxyC1-C6 alkyl, haloC1-C6 alkyl, aminoC1-C6 alkyl, C1-C6 alkyl, cyano, carboxyl, carbalkoxy, carboxamide, carbamoyl, sulfonylamide, benzyloxy, morpholyl-C1-C6 alkyloxy, a monocyclic carbo- or heterocycle, as defined above, a carbo- or heterocyclic group spaced by alkyl, such as C1-3 alkylaryl, etc.
The preferred definitions for Zxe2x80x2 and Zxe2x80x3 include benzyl, unsubstituted or substituted with 1, 2 or 3 substituents, especially 1 selected from fluoro, chloro, hydroxy, amino, xe2x80x94NH(C1-6 alkyl), xe2x80x94N(C1-6 alkyl)2, xe2x80x94NPh(C1-6 alkyl), xe2x80x94NHPh, methoxy, cyano, hydroxymethyl, aminomethyl, alkylsulfonyl, carbamoyl, morpholinethoxy, benzyloxy, benzylamide etc. Other possibilities exhibiting the great freedom in this area are shown in the examples. It will be apparent that the substituent to Zxe2x80x2 and/or Zxe2x80x3 may comprise a ring structure (which substituent ring structure is itself substituted as defined herein) such as phenyl or a 5 or 6 membered heterocycle containing one or two hetero atoms such as thiophene, pyridine etc. The preparation of useful heterocyclic substituents for Zxe2x80x2 and Zxe2x80x3 as benzyl are described in Tetrahedron Letters 1997 6359xe2x80x946359-6367 and J Org Chem 62 (1997) 1264 and 6066, including N-morpholine, N-piperidine, N-piperazine, Nxe2x80x2-methyl-N-piperazine, N-pyrrolidone, N-pyrrolidine and the like.
Such substituents may be in the meta but especially the ortho or para positions of Zxe2x80x2/Zxe2x80x3, with small groups such as fluoro being favoured for the ortho and meta and with extensive freedom for larger groups in the para such as (optionally substituted) cyclic substituents, including the N-bonded rings in the immediately preceding paragraph. The whole Zxe2x80x2 and Zxe2x80x3 group or their respective carbo-or heterocyclic moiety may be different but for ease of synthesis it is convenient if they are the same.
Appropriate pharmaceutically acceptable salts, both for Axe2x80x2/Axe2x80x3 as a free acid or for other charged groups along the compound of formula I include salts of organic carboxylic acids such as acetic, lactic, gluconic, citric, tartaric, maleic, malic, pantothenic, isethionic, oxalic, lactobionic, and succinic acids, organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-chlorobenzenesulfonic acid and p-toluenesulfonic acid; and inorganic acids such as hydrochloric, hydroiodic, sulfuric, phosphoric and sulfamic acids.
Prodrugs of the invention are derivatives that release a compound of formula I in vivo, generally by hydrolysis or other metabolic interaction in the intestine, liver or plasma. Typical prodrugs are esters formed on free hydroxy groups in the compounds. Appropriate pharmaceutically acceptable esters include C1-C22 fatty acid esters, where the fatty acid is unsaturated, monounsaturated or multiply unsaturated. Saturated fatty acid esters include short chains such as acetyl or butyryl or long chain such as stearoyl. Unsaturated fatty acid esters are preferably in the xcfx89-9 series, such as palmitoleic or linolenic esters. Other esters include C1-C6 alkylaryl esters such as benzyl or methylpyridyl or esters of phosphoric acid, such as monophosphate.
Alternative esters include the corresponding fatty acid or alkylaryl carbonate, carbamate or sulphonic esters.
Presently favoured compounds of Formula I include
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3 R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3S,5R)-2,5-di(benzyloxy)-3-hydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,5R)-2,5-di(benzyloxy)-3-hydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)butyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-1-(methylcarbamoyl)-2-phenylethyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-1-(methylcarbamoyl)-2-(4-hydroxyphenyl)ethyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[(4-fluorobenzyl)oxy]-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(cyclopropylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[(2-methylbenzyl)oxy]-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1-[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-N6-[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R,)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2,5-di(2-fluorobenzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2,5-di(4-fluorobenzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2-(benzyloxy)-5-(4-methylbenzyloxy)-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[(4-phenylbenzyl)oxy]-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-thienyl)benzyloxy]-3,4-dihydroxyhexanediamide,
N1,N6-di[(1S)-1-phenyl-1-(methylcarbamoyl)methyl]-(2R,3R,4R,5R)-2,5-di(benzyloxy)-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-(3-fluorobenzyl)oxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2,5-di(3-fluorobenzyloxy)-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-(2-fluorobenzyl)oxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-(2,4-difluorobenzyl)oxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S ,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,4R,5R)-2,5-difluorobenzyloxy)-3,4-dihydroxyhexanediamide
N1, N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5 R)-2,5-di[4-(2,4-pyridyl)benzyloxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-(2,4-pyridyl)benzyloxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[(4-(3-nitrophenyl)benzyl)oxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-2,5-di[4-(2-thienyl)benzyloxy]-3,4-dihydroxyhexanediamide
N1,N6-di[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-(2R,3R,5R)-2,5-di(benzyloxy)-3-hydroxyhexanediamide
N1-[(1S,2R)-2-hydroxy-2,3-dihydro-1H-1-indenyl]-N6-(2-chloro-6-fluorobenzyl)-(2R,3R,4R,5R,)-2,5-di(2-fluorobenzyloxy)-3,4-dihydroxyhexanediamide, and their pharmaceutically acceptable salts and prodrugs.
O-alkylated dilactone intermediates are also novel compounds and thus a further aspect of the invention provides compounds of the formula IV: 
where Zxe2x80x2 and Zxe2x80x3 are as defined above. Preferably the compound of formula IV has the following stereochemistry: 
Favoured compounds of formula IV include those where Zxe2x80x2 and Zxe2x80x3 are benzyl, 2-fluorobenzyl, 2-methylbenzyl, 2,4-difluorobenzyl, 4-fluorobenzyl, 4-bromobenzyl, 4-phenylbenzyl, 4-thiophenylbenzyl, 4-(4xe2x80x2-nitrophenyl)benzyl, 4-(pyridyl)benzyl or benzyl parasubstituted with a primary, secondary or tertiary amine or an N-bonded heterocycle such as piperidine, morpholine etc. Alternatives to benzyl for Zxe2x80x2 or Zxe2x80x3 groups may comprise other arylC1-2alkyl or heteroarylC1-2alkyl such pyridylmethylene, quinolylmethylene or napthylmetylene as known in the P1 protease art.
As with formula I, the Zxe2x80x2 and Zxe2x80x3 groups on the compounds of Formula IV may differ, but it is convenient, and consistent with the bimeric nature of the target enzyme if they are the same.
Preferred intermediate compounds of Formula IV thus include:
2,5-di-O-benzyl-L-mannaro-1,4:6,3-dilactone,
2,5-di-O-(2-fluorobenzyl)-L-mannaro-1,4:6,3-dilactone,
2,5-di-O-(2,4-difluorobenzyl)-L-mannaro-1,4:6,3-dilactone,
2,5-di-O-(4-fluorobenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(2-chlorobenzyl)-L-mannaro-1,4:6,3-dilactone,
2,5-di-O-(4-chlorobenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-thiophen-3xe2x80x2-yl-benzyl)-L-mannaro-1,4:6,3-di-lactone
2,5-di-O-(4-thiophen-2xe2x80x2-yl-benzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(thiazol-4xe2x80x2-yl)-benzyl)-L-mannaro-1,4:6,3-di-lactone
2,5-di-O-(4-thiazol-2xe2x80x2-yl-benzyl)-L-mannaro-1,4:6,3-di-lactone,,
2,5-di-O-(4-phenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-phenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-nitrophenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-cyanophenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-halophenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-aminophenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-carboxyphenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-(4xe2x80x2-phenylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-pyrid-2-ylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-pyrid-3-ylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-N-morpholinylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-N-piperidinylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-N-piperazinylbenzyl)-L-mannaro-1,4:6,3-di-lactone,
2,5-di-O-(4-benzylbenzyl)-L-mannaro-1,4:6,3-di-lactone, and the like.
Intermediate compounds of formula III can be prepared by the following reaction scheme: 
1-amino-azaindan-2-ol P-2 filling groups can be prepared analogously to J Med Chem 1991 1228-1230:
In treating conditions caused by retroviruses, the compounds of formula I are preferably administered in an amount to achieve a plasma level of around 10 to 1000 nM and more preferably 100 to 500 nM. This corresponds to a dosage rate, depending on the bioavailability of the formulation of the order 0.001 to 100 mg/kg/day, preferably 10 to 50 mg/kg/day.
In keeping with the usual practice with HIV inhibitors it is advantageous to co-administer one to three additional antivirals, such as AZT, ddI, ddC, D4T, ritonavir, saquinavir, indinavir, nelfinavir, DMP 266, delavirdine, nevirapine, trovirdine, PFA, H2G etc. The molar ratio for such co-administered antivirals will generally be chosen to reflect the respective EC50 performances of the antiviral. Molar ratios of 25:1 to 1:25, relative to the compound of formula I will often be convenient.
While it is possible for the active agent to be administered alone, it is preferable to present it as part of a pharmaceutical formulation. Such a formulation will comprise the above defined active agent together with one or more acceptable carriers and optionally other therapeutic ingredients. The carrier(s) must be acceptable in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient.
The formulations include those suitable for oral, rectal, nasal, topical (including buccal and sublingual), vaginal or parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. The formulations may conveniently be presented in unit dosage form, e.g. tablets and sustained release capsules, and may be prepared by any methods well known in the art of pharmacy.
Such methods include the step of bringing into association the above defined active agent with the carrier. In general, the formulations are prepared by uniformly and intimately bringing into association the active agent with liquid carriers or finely divided solid carriers or both, and then if necessary shaping the product.
Formulations for oral administration in the present invention may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active agent; as a powder or granules; as a solution or a suspension of the active agent in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water in oil liquid emulsion and as a bolus etc.
With regard to compositions for oral administration (e.g. tablets and capsules), the term suitable carrier includes vehicles such as common excipients e.g. binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, polyvinylpyrrolidone (Povidone), methylcellulose, ethylcellulose, sodium carboxymethylcellulose, hydroxypropylmethylcellulose, sucrose and starch; fillers and carriers, for example corn starch, gelatin, lactose, sucrose, microcrystalline cellulose, kaolin, mannitol, dicalcium phosphate, sodium chloride and alginic acid; and lubricants such as magnesium stearate and other metallic stearates, stearic acid, silicone fluid, talc waxes, oils and colloidal silica. Flavouring agents such as peppermint, oil of wintergreen, cherry flavouring or the like can also be used. It may be desirable to add a colouring agent to make the dosage form readily identifiable. Tablets may also be coated by methods well known in the art.
A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active agent in a free flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative, surface-active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may be optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active agent.
Formulations suitable for topical administration include lozenges comprising the active agent in a flavoured base, usually sucrose and acacia or tragacanth; pastilles comprising the active agent in an inert base such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active agent in a suitable liquid carrier.
Formulations suitable for topical administration to the skin may be presented as ointments, creams, gels, and pastes comprising the active agent and a pharmaceutically active carrier. An exemplary topical delivery system is a transdermal patch containing the active agent.
Formulations for rectal or vaginal administration may be presented as a suppository or pessary with a suitable base comprising, for example, cocoa butter or a salicylate. Other vaginal preparations can be presented as tampons, creams, gels, pastes, foams or spray formulations containing, in addition to the active agent, such carriers as are known in the art to be appropriate.
Formulations suitable for nasal administration wherein the carrier is a solid include a coarse powder having a particle size, for example, in the range 20 to 500 microns which is administered in the manner in which snuff is taken, i.e. by rapid inhalation from a container of the powder held up close to the nose. Suitable formulations wherein the carrier is a liquid for administration, for example, as a nasal spray or as nasal drops, include aqueous or oily solutions of the active agent.
Formulations suitable for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain antioxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injection, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets of the kind previously described.
The invention will now be further illustrated by reference to the following non-limiting Examples.